linux-kernel - Re: [PATCH 3.4-rc] KVM: VMX: Fix kvm_set_shared

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Date:	Wed, 18 Apr 2012 23:42:44 -0300
From:	Marcelo Tosatti <mtosatti@...hat.com>
To:	Avi Kivity <avi@...hat.com>
Cc:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org, davej@...hat.com
Subject: Re: [PATCH 3.4-rc] KVM: VMX: Fix kvm_set_shared_msr() called in
 preemptible context

On Wed, Apr 18, 2012 at 03:03:04PM +0300, Avi Kivity wrote:
> kvm_set_shared_msr() may not be called in preemptible context,
> but vmx_set_msr() does so:
> 
>   BUG: using smp_processor_id() in preemptible [00000000] code: qemu-kvm/22713
>   caller is kvm_set_shared_msr+0x32/0xa0 [kvm]
>   Pid: 22713, comm: qemu-kvm Not tainted 3.4.0-rc3+ #39
>   Call Trace:
>    [<ffffffff8131fa82>] debug_smp_processor_id+0xe2/0x100
>    [<ffffffffa0328ae2>] kvm_set_shared_msr+0x32/0xa0 [kvm]
>    [<ffffffffa03a103b>] vmx_set_msr+0x28b/0x2d0 [kvm_intel]
>    ...
> 
> Making kvm_set_shared_msr() work in preemptible is cleaner, but
> it's used in the fast path.  Making two variants is overkill, so
> this patch just disables preemption around the call.
> 
> Reported-by: Dave Jones <davej@...hat.com>
> Signed-off-by: Avi Kivity <avi@...hat.com>
> ---
>  arch/x86/kvm/vmx.c |    5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)

Applied, thanks.

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